I take mine in for a couple of reasons. First, I connect my air compressor line to the pipe that connects to the output side of the BFP. Second, although there are other ways to connect the air, I am always a bit concerned that maybe just a tad bit of water might remain in the BFP and cause a problem. I connect the BFP with 1" copper unions, so it isn't a major undertaking to R&R it. I made an adapter with half of a 1" union, a 1" nipple, a reducer to 1/2", a 1/2" ball valve, a nipple and a reducer to an air quick connector that my air hose snaps on to. I blow 1 zone at a time using 2 sixty gallon tanks of air each. I shut the ball valve while the tank is refilling. I never turn the air into the line when the zone valve is closed. This is a bit slower than the yard services with the huge industrial compressors, but they charge $50 so if it takes me 2 hours, that's $25 an hour for my time. I usually put the BFP back in about the 1st of March, then it's ready for it's annual certification inspection whenever the technician is in the neighborhood.

I live in North Carolina and have an below ground BFP that is 12 below ground in an insulated box. Our typical frost layer is 6 inches and a max of 12 in sever winter. ( Have not w=seen this in over 10 years.)

I just close the valve before the BFP, blow out the system, and that is it.